In a typical electrical distribution system, electrical energy is generated by an electrical supplier or utility company and distributed to consumers via a power distribution network. The power distribution network is the network of electrical distribution wires that link the electrical supplier to its consumers. Typically, electricity from a utility is fed from a primary substation over a distribution cable to several local substations. At the substations, the supply is transformed by distribution transformers from a relatively high voltage on the distributor cable to a lower voltage at which it is supplied to the end consumer. From the substations, the power is provided to industrial users over a distributed power network that supplies power to various loads. Depending on the specific needs of the users, these loads can include, for example, various power machines, lights, HVAC units, and other types of equipment.
At the consumer's facility, there will typically be an electrical energy meter (“revenue meter”) connected between the consumer and the power distribution network so as to measure the consumer's electrical demand. The revenue meter is an electrical energy measurement device that accurately measures the amount of electrical energy flowing to the consumer from the supplier. The amount of electrical energy measured by the meter is then used to determine the amount for which the energy supplier should be compensated. Typically power meters are designed and calibrated to cover circuit transformer specifications.
Cogeneration and independent power providers (IPP) applications have two modes of operation: In generation mode, a high amount of energy is flowing out of the facility. Typically 2 amps to 20 amps or more current generated at the secondary of the current transformers (CTs). When generation is turned off, those facilities behave as tiny loads, with as little as 0.010 amps to 0.015 amps being generated by the CTs. Measuring the bi-directional energy flow is usually done with two meters, one that will be able to measure accurately the high generation current but will not measure accurately in the low range, and one that will be accurate for the low load current, but will saturate in generation mode. Accordingly, there is a need to reduce the cost and complexity of installation hardware at these sites in addition to reducing the complexity of interpreting the energy readings from both meters.